Cross reference
Exodus 15:23
23 and they come in to Marah, and have not been able to drink the waters of Marah, for they `are' bitter; therefore hath `one' called its name Marah.
Numbers 33:8
8 And they journey from Pi-Hahiroth, and pass over through the midst of the sea, into the wilderness, and go a journey of three days in the wilderness of Etham, and encamp in Marah.
Ruth 1:20
20 And she saith unto them, `Call me not Naomi; call me Mara, for the Almighty hath dealt very bitterly to me,